改进的锯齿形光谱滤波器

Modified jammed-array wideband sawtooth filter

锯齿形光谱(JAWS)滤波器的光谱成分比较复杂,是一种较难实现的光谱滤波器。本文通过数值仿真对基于虚像相位阵列(VIPA)的JAWS滤波器的主要参数如线性度、占空比和信噪比(SNR)等进行了优化,并进行了实验验证;通过对JAWS滤波器插损的分析,将反射式的工作方式改变为透射式的工作方式,使整个滤波器的附加损耗从20dB减小到小于6dB;同时,滤波器的性能也有了明显的进步。

Jammed-array wideband sawtooth （JAWS） filter has periodic multi-channel sawtooth spec- trum. Due to the complex spectral components, it＇s difficult to make a passive multi-channel sawtooth fil- ter. In this article,we present a modified JAWS filter with low loss. It only consists of four elements,in- eluding a fiber collimator, two lenses and a virtually-imaged phased array （VIPA）. The beam transmitted through the VIPA is collected by a lens and a large area photodetector rather than a mirror is used to re- flect the beam back into the fiber. The extra insertion loss is lower than 6 dB and the performance of the filter is much better than that of the JAWS filter with beam reflected by a mirror. The main characteris- tics of the jammed-array wideband sawtooth filter based on a virtually-imaged phased array are studied systematically. The main parameters, such as linearity, duty cycle and signal-to-noise ratio,are optimized by numerical simulation and tested by the experiment. Since the free spectrum range of the filter is decid- ed by the thickness of VIPA,the optimization of VIPA with different thicknesses is also discussed. The filter might be used in fast sensitive interrogation of concatenated multi-channel fiber Bragg grating sen- sors and ultra-high-frequency electrical sawtooth waveform generation.